The post-harvest losses of fruits and vegetables, which are quickly perishable, are a major cause for concern in developing countries because of the fact that a large amount of what is produced never reaches to the consumer. This loss in India, the second largest producer of fruits and vegetables, account for 35-40% of total produce; a loss estimated at 40,000 crores per year, directly affecting economy. The main factor in determining the post-harvest deterioration of fruit and vegetable crops is the rate of softening, which influences shelf life, wastage, infection by post-harvest pathogens, frequency of harvest, and limits transportation and storage, all of which directly affect costs. Attempts to understand molecular basis softening is focused on cell wall metabolism and tomato has provided the principal model system for these studies. However, decreased expression of several proteins acting on cellulose, hemicelluloses and pectin polysaccharides in transgenic tomato fruit has proven to be insufficient to prevent fruit softening [Brummell D A, Harpster M H (2001) Plant Mol Biol. 47:311-340 and Giovannoni J (2001) Annual Review of Plant Physiology and Plant Molecular Biology 52: 725-749], suggesting that modifications of these cell wall components are not the sole factors to determine fruit firmness.
N-Glycoproteins are one of the constituents of plant cell wall and free N-glycans are also reported to occur in tomato fruit. Moreover free N-glycans are known to induce tomato fruit ripening and blocking of N-glycosylation with tunicamycin delayed fruit ripening, which suggests that N-glycoprotein processing is important in ripening process [Priem B, Gitti R, Bush C A, and Gross K C (1993) Plant Physiol. 102: 445-458]. Most glycoprotein of plant source contain substantial amount of paucimannosidic N-glycans, which is produced by the removal of terminal GlcNAc residues in the secretary pathway as a consequence of β-D-N-acetylhexosaminidase activity (Strasser R, Bondili J S, Schoberer J, Svoboda B, Liebminger E, Glo{umlaut over ( )}ssl J, Altmann F, Steinkellner H and Lukas Mach (2007) Plant Physiology 145: 5-16.). Moreover, β-D-N-acetylhexosaminidase shows consistent increase in activity during ripening of tomato and capsicum and is present in banana, mango, papaya, etc. (Jagadeesh B H and Prabha T N (2002) Phytochemistry, 61(3): 295-300; and Jagadeesh B H, Prabha T N and Srinivasan K (2004) Plant Science 166(6): 1451-1459).